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Measurement of Bc in CDF

Measurement of Bc in CDF. Ilsung Cho Yonsei University , Seoul Korea. The 1 st day of Universe ……. ? ? ? ? ?. In the beginning God created the heaven and the earth. And God said: 'Let there be light.' And there was light. - Genesis chapter 1. What is the world made of?

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Measurement of Bc in CDF

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  1. Measurement of Bc in CDF Ilsung Cho Yonsei University , Seoul Korea

  2. The 1st day of Universe …… ? ? ? ? ? In the beginning God created the heaven and the earth. And God said: 'Let there be light.' And there was light. - Genesis chapter 1

  3. What is the world made of? What holds the world together? Where did we come from?

  4. Standard Model Particle physics field has been tremendously successful in creating and establishing “Standard Model of Particle Physics”answering ”what the universe is made of” and “how it works”.Answers themselves led to even more questions

  5. Elementary Particles top quark anti-top quark ne nm nt e-mt u d s c b . . . . - - - - - - - - ne nm nt e+mt u d s c b Z W+, W- ( Mass proportional to area shown: proton mass = ) gluons Are they the smallest things? Why are there so many? Where does mass come from?

  6. Galaxies are held together by mass far bigger (x5) than all stars combined. Everything is made of electrons, u quarks and d quarks Dark Matter ???

  7. Questions remained unsolved yet ……. 1. Are there undiscovered principles of nature: New symmetries, new physical laws? 2. How can we solve the mystery of dark energy? 3. Are there extra dimensions of space? 4. Do all the forces become one? 5. Why are there so many kinds of particles? 6. What is dark matter? How can we make it in the laboratory? 7. What are neutrinos telling us? 8. How did the universe come to be? 9. What happened to the antimatter? Origin of Mass Unification Energy Frontier Colliders

  8. Hadron Collider

  9. CM frame : Synchrotron radiation Boost factor Collider Parameters : Energy Total E2 : Energy limit :

  10. Collider Parameters : Luminosity The number of particles passing each other Defined as unit area x unit time x unit transverse area 1year ~ px107sec time to operate ~1year/ p

  11. The World’s highest energy • hadron collider 36 proton and antiproton bunches 396 ns bunch crossing  2.5Mhz Instantaneous Luminosity : 1.2 x1032cm-2 s-1

  12. Event identifying tool : Detector & Trigger

  13. Our EYE : Detector Use cylindrical coordinate Pseudo rapidity h R h =1 h =-1 45 degree Z Z direction : normally choose beam direction

  14. Our EYE : Collider detector Particle detection is based on its interactions with matter of the detectors Stable particle( interacting particle) :P, e, K, p, m, g Modern multipurpose collider detector

  15. Muon chamber Calorimeter Solenoid coil Time of Flight Central Outer Tracker Silicon vertex detector • Inherited from Run I • Central Calorimeter (|η|<1) • Solenoid (1.4T) • Partially new • Muon System (extended upto |η|~1.5) • New • Tracking System • - 3D Silicon Tracker (up to ||~2) • - faster Drift Chamber • Plug and Forward Calorimeters • Time-of-Flight (particle ID) • Luminosity monitor • DAQ system, front end electronics • Trigger system (new trigger on • displaced vertices!)

  16. J/y  m+m- CDF dimuon trigger 1st track : Track+Muon 2nd track :Track+Muon opposite charge Invariant mass • The World’s highest energy • hadron collider 36 proton and antiproton bunches 396 ns bunch crossing  2.5Mhz 250kB per 1 events with 2.5Mhz  625GByte/sec !!!!!! Instantaneous Luminosity : 1.2 x1032cm-2 s-1

  17. Trigger large bandwidth, background suppression, deadtimeless Level1 Hardware trigger designed to find physics object Level2 Hardware trigger to do a limited event reconstruction Level3 A processor farm. It uses the full detector resolutions to fully reconstruct evemt

  18. Heavy flavor physics “Heavy” flavors, defined as b & c quarks, not t, which is heavier, as the top doesn’t live long enough to form a meson and just decays ~100% directly to b quarks

  19. The CKM Matrix Unitary with 9*2 numbers  4 independent parameters Many ways to write down matrix in terms of these parameters

  20. The Basics: Quark Mixing & the CKM Matrix d s b mass u c m a s s t A, l, r and h are in the Standard Model fundamental constants of nature like G, or aEM h multiplies i and is responsible for CP violation We know l=0.22 (Vus), A~0.8; constraints on r & h

  21. c c Best measured in Bs decays g b a The 6 CKM Triangles Area of each = A2l6h, the Jarlskog Invariant There are 4 independent phases: b, g, c, c (a can be substituted for g or b, as a+b+g=p)

  22. ‾ The Bc is a ground state of bc system 1st experimentally observed by CDF (PRL 81 1998)  Mass measurement Test of QCD calculation and new potential models  Lifetime measurement Information on both masses of c and b quarks. : large uncertainty on theoretical calculation, 0.4~0.7ps, due to uncertainty of quark mass provide information on the formation of the bound states of two heavy quark.  Spectroscopy of excited states : Possible observation, test of QCD calculation

  23. b g b g g q q q b b b b b-quark production at TEVATRON b q b g g g Flavor Creation (annihilation) Flavor Creation (gluon fusion) Gluon Splitting Flavor Excitation Tevatron is a source of all B-hadrons, Bd, Bu, Bc, Bs and Λb sb = 29.4 ± 0.6 ± 6.2 mb (|η| < 1) (CDF), Huge cross-sections, but large BKG

  24. b g BC g c Production and Decay of Bc Gluon-gluon fusion is the dominant process for Bc production Production cross section of Bc is an order of 10-3 of B+ S.S Gershtein,et el..,”Theoretical Status of the Bc Meson” c-quark decay with the spectator b-quark (cX) b-quark decay with the spectator c-quark(bX) The annihilation channel

  25. Semileptonic channel p e,m, u, … ne, nm, d, … c c J/y b c Bc m+m-

  26. Which information is needed ? Semileptonic decay has a large branching fraction BcJ/ye u, J/y m mchannel : 3 track topology • Muon system J/ymm trigger • Calorimeter • Electron ID • Tracking system (COT) • High efficiency tracking • dE/dx for electron ID • Tracking system (Silicon) • Good vertex resolution Muon detector + Tracker Muon Muon EM calorimeter+Tracker electron Electron neutrino Bc decays in the beam pipe line Anti proton Proton

  27. YES NO J/y+ not real electron Some hadrons minic e signature in detector  Fake electron BKG OK !! Revised flowchart Starting point : J/y + track ( electron candidate) Reconstruct J/y we will use J/y signal area J/y + TRACK Where the track comes from ? Is the track is real electron ? Do the electrons come from Bc ? J/y+ real e , BUT e is NOT from Bc e from pair production  Residual conversion BKG e from the other side of b meson decay  BBbar BKG

  28. Key elements for Bc analysis Kinematical signature : 4<M(J/y+e)<6, good J/y+e vertex Background estimation Fake electron • Estimate fake rate( K/p/p electron in detector) • Use J/y+track data as control sample and apply fake rate Electron from Photon conversion • Estimate conversion finding efficiency • Use J/y+ (electron from conversion) data • Get residual conversion background B-Bbar background • PYTHIA MC simulation ( bJ/yX and bbareX) • Get the contribution from the other side of b-quark

  29. Headache to analyze data 2 years ago xpmmod: 360pb-1 around 1 Tera B , 19 Million events : 1week Reconstruct J/y+ any track combination xbhd0d : 360pb-1 around 11TeraB , 216 Million events : 2month …… Reconstruct D* D0 p mode L0 Pp mode Ks pp mode blpc0d : 360pb-1 around 3TeraB , 31 Million events : 1 week Reconstruct g e+ e- mode Most headache  simulation 1events took 6 minutes about 2 years ago at my linux box 10events/1hour  240 events /day  85,540 events/1year At least I needed 1Million events , 10 year !!!!!!! 10 million events  100 year for 1 CPU

  30. Fake electron background Fake rate for p/K/P from data Averaged using MC particle fraction Expected background  15.430.31(stat.)2.52(syst.)

  31. g conversion background Photon conversion candidates are removed by finding partner track during electron ID Conversion finding efficiency from Monte Carlo Expect J/y+residual conversion background from J/y+tagged conversion data 14.544.38(stat.)6.39(syst.)

  32. BBbar background Calculate the number of b-bbar background • Normalize to data using B+ • Apply electron reconstruction efficiency Eff(eID)X Eff(dE/dx)~63% Expected background 33.632.20(stat.)11.17(syst.) The biggest systematic error due to different PDF,ISR setting Will be improve by measuring B-Bbar correlation in Run2

  33. Bc signal candidates Background : 63.64.9(stat.)13.6(syst.) Observed : 178.514.7(stat.) Excess : 114.915.5(stat.) 13.6(syst.) Significance : 5.9s

  34. Bc measurement : Cross section , Lifetime & Mass

  35. Cross section We choose to use pT(Bc)>4, |y(Bc)|<1 as our definition

  36. Cross section Cross section ratio is defined within our kinematical limits pT(B) > 4.0GeV , |y(B)| < 1.0 • RK : Kinematics acceptance ratio • =4.420.08(stat.)1.02(syst.) • Re : Electron reconstruction ratio • = 1/e(eID) 1/(63%) • N(B+)=2872  59 sratio=0.2820.038(stat.)0.035(yield)0.065(acceptance)

  37. Muon Muon electron Electron neutrino Lxy Secondary vertex Anti proton Proton Primary vertex Pseudo-proper decay length Lifetime measurement Because of undetectable neutrino we cann’t calculate Bc momentum directly Use MC simulation and the reconstructed momentum of J/y-e pair to estimate Bc momentum (K-factor) Where a is the angle between the vector of pT(J/y+e) and pT(Bc)

  38. Background shape determination Fake electron : J/y+track with electron fake rates Fake J/y: Sideband in J/y+track candidates Residual conversion : J/y+tagged conv. electron with conversion finding efficiency b-bbar : PYTHIA MC but with change of GS/FE/FC for systematic error Prompt : Assume to be a resolution function

  39. Background shape determination Fake electron Fake J/y Residual conversion bbBAR

  40. Lifetime fitting result • ct(Bc)  = 139.0 +22.1/-19.5 (stat.) 10.8 (syst.) mm • t(Bc) =0.463 +0.073/-0.065(stat.) 0.036(syst.) ps

  41. Hadronic decay channel p e,m, u, … ne, nm, d, … c c J/y b c Bc m+m-

  42. Which information is needed ? BcJ/y p, J/y mm channel : 3 track topology Precise mass measurement possible Muon system J/ymm trigger Calorimeter Electron ID Tracking system (COT) High efficiency tracking dE/dx for electron ID Tracking system (Silicon) Good vertex resolution Muon detector + Tracker Muon Muon Tracker p Need aggressive 2nd vertex resolution to reduce backgrounds Bc decays in the beam pipe line Anti proton Proton

  43. Muon Muon Key elements for Bc analysis Search range : 6.4 +- 2s5.6 to 7.2 GeV Backgrounds : Prompt J/y + track from PV B-Bbar background Muon Muon B+ B0 • Cut optimization : • Signal from MC and background from data, choose max significant point Tight vertex requirements

  44. 0.36 fb-1 ~0.5 fb-1 ~0.6 fb-1 ~0.7 fb-1 ~0.8 fb-1 Bc J/ypreconstruction Num(events)FIT= 38.9 sig 26.1 bkg between 6.24-6.3 Significance > 6s over search area Mass = 6275.2 ± 4.3(stat.) ± 2.3(syst.) MeV/c2

  45. Summary Cross section ratio between Bc+J/ye+n and B+J/yK+ for pT(B)>4GeV, |y(B)|<1 range : sratio=0.2820.038(stat.)0.035(yield)0.065(acceptance) Lifetime : WORLD BEST MEASUREMENT !!!! • ct(Bc)  = 139.0 +22.1/-19.5 (stat.) 10.8 (syst.) mm • t(Bc) =0.463 +0.073/-0.065(stat.) 0.036(syst.) ps Mass : 6275.2 ± 4.3(stat.) ± 2.3(syst.) MeV/c2 S.Godfrey RR D 70, 054017  mass of 6271 GeV V. V. Kiselev, hep-ph/0308214 (2003) : 0.55ps+- 0.15ps

  46. Do we need more physics ???

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